This invention relates to wound fiber oxygenators, and more specifically to a method and apparatus for improving the blood-fiber contact by disrupting the laminar flow of the blood across the fibers.
A common form of blood oxygenator used in heart-lung machines consists of many layers of microporous hollow gas-exchange fibers wound at an angle around a generally cylindrical core. Oxygen is made to flow longitudinally through the hollow fibers, and blood is caused to flow across the fibers. The material of the fibers is such that whenever a blood cell contacts a fiber, an oxygen-carbon dioxide exchange takes place between the cell and the inside of the fiber.
Because the efficiency of the oxygenator depends on the number of blood cells that contact the fibers, it is desirable to thoroughly mix the blood as it flows across the fibers. This assures that the maximum number of blood cells will have a chance to get close enough to a fiber for a successful gas exchange at some point during their transit through the oxygenator.
In conventional fiber-wound oxygenators, such thorough mixing is, however, difficult to achieve. Although the fibers are wound in opposite directions in successive layers so that they cross each other, the geometry of such windings is such that channels exist in which blood can flow laminarly all the way through the fiber bundle. Even where the blood flow encounters a fiber, the flow typically divides to flow across opposite sides of the fiber, and then recombines back into a generally laminar flow.
The present invention increases mixing of the blood in a wound fiber oxygenator by disrupting laminar blood flow through the channels formed by the winding pattern of the fibers. This is accomplished in the invention by periodically inserting, between two successive layers of fibers, a generally flat, ribbed apertured sheet of plastic. Such a sheet is preferably composed of a gridwork of solid ribs running at right angles to each other in a common plane.